"There weren't enough portaloos, so our council officers were going into flats in the morning where the workers had been using them as toilets, and continue to use the entrance hall to their flats as a toilet," Ms Shurey said.

"I couldn't live there and I know any of you would have difficulty."

Inquiry committee member and Labor MP Courtney Houssos says the issues show the project has been "mismanaged from the beginning".

"When most of the zones are in delay for hundreds of days, the idea that the contract was formed only providing for 15 is ridiculous," Ms Houssos told AAP.

Appearing before the inquiry, NSW Auditor-General Margaret Crawford said two oversights made by the government during the planning process contributed to the $500 million-blowout.

"They were two very important stages that were missed," Ms Crawford said.

Those two stages were a business case and a strategic assessment gateway review.

"The conclusion that I reached was that during that period Transport for NSW did not effectively manage the planning and procurement process to ensure that NSW had value for money for the project."

The light rail, linking the CBD to the city's eastern suburbs, was originally budgeted at $1.6 billion.

A series of delays and contractor disputes have pushed the estimated price to $2.1 billion.

Asked whether she was concerned about the inquiry, Premier Gladys Berejiklian described the light rail as an "amazing project".

"I'm not concerned at all ... it's going to positively change Greater Sydney forever for the better and I can't wait for it to open and we're working hard to make sure that happens," she told reporters.